I am pretty sure its the hero of Kvatch and Sheogorath are one in the same as he even makes references of being around and about at the oblivion crisis and he mentions martian
Most likely the Champion of Cyrodiil, but he is the wrong race. He is suppose to be a Imperial, not a Breton. :l
My champion of Cyrodiil was a Dunmer lady. So yeah...a bit of an awkward moment there.